The England captain Rio Ferdinand talks to fans before the squad flew out to South Africa. Photograph: Clive Gee/PA

Rio Ferdinand claims none of the England squad felt safe as Fabio Capello prepared to drop seven players from his party and the captain added that the lack of a comfort zone will help drive the players as they try to win the World Cup in South Africa.

Ferdinand admitted that in years gone by England players with big reputations expected to retain their places, even if they had "two or three bad games". But after the Italian made Theo Walcott the most high-profile and surprising omission from the 23-man squad that set off for South Africa tonight, the players took on board a sobering message.

"No one's safe in this squad, as the manager has shown by leaving Theo out," Ferdinand said. "The manager isn't scared to leave out people with big reputations if he feels they won't have a positive impact on the squad. He doesn't care about reputations. It wouldn't have been a surprise if anyone had been left out of the squad, other than Wayne Rooney.

"Reputations may have got in the way in the past, but it is difficult being the England manager. You have to be experienced and a strong character to deal with the pressure, and he [Capello] deals with everything in the right way.

"It's impossible to second-guess the manager, to know what he is thinking. There's no room for complacency, perhaps that's a better way of putting it. You can't say to yourself, 'If I have two or three bad games, I'm still going to play,' which was the attitude of some in the past."

Walcott's omission reminded Ferdinand of one of his lowest moments, when Kevin Keegan dropped him from England's Euro 2000 squad. "It was the worst feeling in the world," he said. "But I looked at every aspect of myself and my career and I told myself I had to step up. I'm sure Theo will go away and work hard to hit the manager back between the eyes and make sure he's part of the next squad."

Capello has said that if his players perform in South Africa as they do for their clubs in the Premier League, they will reach the final on 11 July and Ferdinand is keen to set down psychological markers in the early matches.

"If we play to our potential, all together, then we will be a hard team to play against and I think that's the most important thing," added Ferdinand, speaking at Nike's No More Talk event. "We want teams not to want to draw us. If you can get that kind of level in your play, even before you go out on to the pitch, you're in a stronger position. At past tournaments, teams weren't too bothered about getting us but hopefully, when this tournament starts and we play a couple of games, teams will change that opinion."

Ferdinand, 31, has been in England's previous three World Cup squads and this time he is determined to return with no regrets. "There have been too many times at past tournaments when that has been the case," he said. "I don't want to finish my England career – I hear people are saying this is my last tournament – like that.

"The message is that we are going to be doing our utmost to try and bring this cup back. We are not there to finish second. Or to get into the semi-finals and think that we did a good job because we got past the quarters. We are there to win it."

England boarded the flight to South Africa having been boosted by a display of commitment from Capello. There had been a break clause in his managerial contract, signed when he took the job in December 2007, which allowed either himself or the Football Association to sever the deal, at a cost of £6m, during a two-week window after the World Cup.

Much was made of this last week in the wake of Internazionale's desire to sign Capello, but the Italian met the Club England chairman Sir Dave Richards at Wembley today to have the clause removed. Capello is now committed to staying until the 2012 European Championship. "I am very happy about this and would like to thank Sir Dave Richards and the FA for their continued support and assurances," Capello said. "I always wanted to stay until the end of my contract [in 2012]."